Doctor… Is There A Link Between Breast Cancer and Osteoporosis?

Osteoporosis is a metabolic disease where bones lose their mineral content (primarily calcium) and becomes more prone to fracture.  Osteoporosis may cause fractures at any site but the most common are the vertebrae (spine), hip, and wrist.

Both breast cancer as well as some of the treatments used against this disease may increase the risk for osteoporosis. Here are a few of the reasons for the link between breast cancer and osteoporosis:

• The disease itself. Breast cancer causes an increase in the activity of osteoclasts.  These are the cells that remove old bone.  If the rate of removal exceeds the rate that new bone is made, then the end result is bone loss.
• Weight loss occurs as a result of the cancer.  This leads to less gravitational stress on the skeleton.  The stress of gravity actually helps maintain bone mass (that is why astronauts who’ve been in a weightless environment will lose bone mass).
• The treatment.  Chemotherapeutic drugs (the most common ones being methotrexate, 5-fluorouracil, and cyclophosphamide) shut down the function of the ovaries.  Because the ovaries no longer produce estrogen, a condition of early menopause is induced.  Bone loss occurs because estrogen is an important bone protective hormone.
• High doses of corticosteroids are also used in many cases to treat breast cancer.  Among the side effects of steroids is bone loss.
• Another treatment which is surgical removal of the ovaries (oophorectomy) also leads to loss of ovarian function.  Radiation therapy is sometimes given for breast cancer.  This also can result in cessation of ovarian function.  These procedures are done to slow breast cancer growth since some breast cancers are stimulated by estrogen.  As with chemotherapy, there is lowering of estrogen levels with loss of ovarian function.  The consequence is loss of bone mass.
• Other therapies can also cause bone loss.  Newer hormonal therapies using aromatase inhibitors (anastorzole, letrozole, etc.)  are used for postmenopausal women with breast cancer. Some evidence exists that these drugs also have the potential to cause bone loss. Other hormonal treatments such as leuprolide and goserelin can stop ovarian function in premenopausal women, leading to a reduction of estrogen production.  This, of course, then causes bone loss.

So what can be done in a situation like this to prevent bone loss?   Here are some tips:

• Maintain an adequate amount of dietary calcium (1,000 milligrams for premenopausal and 1,500 milligrams for postmenopausal women), as well as a daily dose of vitamin D between 400-800 international units. Sometimes higher doses are required in patients who are vitamin D deficient.
• Regular weight bearing exercise such as walking, jogging, and climbing stairs.
• Strength training exercises for the arms and upper body. Either lightweight dumbbells or other weight resistance devices will work.
• Flexibility exercises such as stretching, yoga, t’ai chi.
• Discontinue cigarettes.
• Reduce alcohol intake.
• Consult a physician specializing in osteoporosis.  They will probably want to evaluate your bone density and make certain suggestions.

Medications designed to reduce bone loss also may be necessary.  These include bisphosphonate drugs (alendronate, risidronate, ibandronate) and selective estrogen receptor modifiers (SERMS) such as raloxifene.